#include <iostream>
using namespace std;

int main(int argc, char const *argv[])
{
  int a = 10;
  int &b = a;

  // 1. 引用必须初始化
  // int &b; // declaration of reference variable 'b' requires an initializer

  // 2. 引用初始化后不可以改变
  int c = 20;
  b = c;  // 赋值操作，不是更改引用

  cout << "a = " << a << endl;
  cout << "b = " << b << endl;
  cout << "c = " << c << endl;

  return 0;
}